Plasticized polyvinyl chloride (PVC) tubing has been utilized in the medical field for many decades. Over this time period, there have been various post tube manufacturing operations utilized to apply fitments at the end of the tube so as to incorporate the tube into various medical assemblies, e.g., connected to an insulin pump or the like, or to a delivery member (e.g. needle set) for the delivery of fluids to a patient (human or other animal) for health maintenance or during operational procedures. Typically, these various fitments include a region where the tube is inserted into the fitment and it is then secured (e.g., by adhesives or other chemical and non-chemical bonding means) in liquid-tight engagement to the fitment. Fitments may be made from various materials, including acrylonitrile-butadiene-styrene (ABS) copolymers, polycarbonate (PC), acrylic resins and other thermoplastic materials so chosen for their mechanical properties, thermal stability and for the ability to be precisely molded within very tight dimensional tolerances.
During the assembly process of combining a tube with a fitment, there is a stage where a bonding material, such as a UV curable adhesive material, is applied with an applicator to the external outer surface of the tube, and the tube is then physically engaged into the fitment. At the conclusion of fitting the tube into the fitment, this portion of the assembly is exposed to UV (ultraviolet) light which activates the adhesive to cure into a final solid form and the tube is adhesively bonded to the fitment. The nature of the bonding which occurs is such that it takes a certain amount of force to physically remove the tube portion from the fitment, e.g., to prevent unintended dislodgement during use of the assembly. This force is typically much larger after the application and curing of the adhesive to the surfaces versus simply a physical insertion of the tube into the fitment, in the absence of the adhesive.
Plasticized PVC tubing has been demonstrated to be most useful for all of these operations with a variety of fitments made from the different materials types referenced above. However, for at least environmental, regulatory and/or legislative reasons, there is a need to avoid the use of plasticized PVC as the material with which to make medical tubing. The potential for migration of the plasticizer into the medicinal fluid has been cited as a concern for some fluid types.
Other elastomeric materials also have chemical functionality (esters, amide, etc.) that may have interactions with various medicinal fluids. Thus, there is a need to provide a secure bonding that does not require chemical functionality in the tube or fitment that may potentially interact with the fluid being delivered by the assembly.
Medicinal fluids—not just the solvent/fluid types, but the medicinal fluid itself, may comprise balanced/stable colloids and suspensions of the active pharmacological agents that are buffered with surfactants and other dispersion/suspending agents. These agents may preferentially adsorb to chemical functionalities of the tube material/luer and thus affect the medicinal efficacy of the fluid.
Still further, many of the common fitment materials (ABS, PC, and acrylics) are amorphous materials that are subject to crazing/cracking. Thus the ABS, PC, Acrylic, etc luers in common usage today may have molded in stress which makes them especially susceptible to cracking in the presence of solvents, either prior to or during use. The nature of the medicinal fluids may cause stress cracking of such amorphous materials or changes in dimensions of the luers that cause leakage or failure.
Thus, there is an ongoing need for new tubing and fitment assemblies that avoid the aforementioned problems of stress cracking, chemical interactions, and processing difficulties of the prior art.